Die fixture



p 41- I H. G. GROEHN 2,256,247

I DIE FIXTURE Filed Aug. 23, 1940 INVENTOR flan 6? Graalvz ATTORNEYi Patented Sept. 16, 1941 UNITED STATES PATENT OFFICE Harvey G. Groehn, Trenton, Mich. Application August, 1940, Serial No. 353,872

7 Claims.

This invention relates to fixtures for checking the various dimensions of stamping and forming dies.

This method of forming checking fixtures is both time consuming and expensive, and the fixtures thus formed are not so accurate as is frequently desired because there are too many possibilities of' error since each portion of the checking fixture has to be independently shaped by hand in an effort to make its shape conform with the contour of the master wood model.

My invention overcomes many of the disadvantages of the method heretofore employed in making checking fixtures because it is unnecessary to fit any portion of the female fixture to the male master. A frame having the general contour of the master male model is fabricated by joining together segments of wood or other suitable material to conform generally to the contour of the master male model. The ends of the pieces of wood forming the framework preferably lie adjacent the surface of the master male model, but considerable variation in dimensions is permitted because low melting alloy of the Wood's metal group may be introduced between the surface of the master model and the ends of the segments forming the framework of the checking fixture. The space between the surface of the master model and the ends of the frame-' work of the checking fixture may vary through relatively wide limits, being preferably between a; of an inch and of an inch.

Checking fixtures made in accordance with this method accurately .conform to the exact shape of the master model and may be produced quickly and economically.

An object of this invention is therefore to provide a checking fixture which may be quickly and economically produced and which accurately con-.

forms to the shape and dimensions of the master model. i

Another object of the invention resides in the provision of an improved checking fixture particularly adapted for checking trim lines, pierced holes, flange lines, spotting the shape or contour to a male punch casting,

and laying out orlo'cat tended to limit the invention claimed ing the dimensions and sizes of the die in their proper relation to the finished part. w

A further object of this invention is to provide a female checking fixture having removable inserts which when in place may be used as a finished or master female duplicate model.-

A still further object resides in the provision of a female checking fixture having removable inserts which in the assembled condition gives a full female or opposite surface to the master model which may be advantageously used in Kellering female pads and spotting male punches.

Another object resides in the provision of an economical checking fixture which may be. readily employed for checking various dimensions of dies and other parts in the event that the master models are not available.

Other objects and advantages of this invention will be apparent from the following detailed description considered in connection with the accompanying drawing, submitted for purposes of illustration only, and not intended to define the scope of the invention, reference being had for that purpose to the subjoined claims.

In the drawing wherein similar reference characters refer to similar parts throughout the several views:

Fig. 1 is a plan view of a checking fixture embodying the present invention.

Fig. 2 is a sectional view taken substantially on the line 2-2 of Fig. 1.

Before explaining in detail the present invention it.is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawing, since the invention is capable of other embodiments and'of being practiced or carried out in various ways. Also it is to be understood that the phraseology 0r terminology employed herein is for the purpose of description and not of limitation, and it is not inherein beyond the requirements of the prior art.

' Referring now more particularly to the drawing, it will be observed that a checking fixture 8 which, by way of example, may be employed to check the die used in the formation of a rear vehicle door, is illustrated. As more clearly illusrately conforms to the desired shape of the part to be formed. The master male model 10 is shaped toembody the desired contour for a rear vehicle door having a window opening II.

In the formation of the checking fixture a framework comprising longitudinal and transverse members l4 and I6 respectively may be positioned to overlie the master male model l0.

and any suitable number of longitudinal and transverse reinforcing and checkingribs l8 and '20 respectively may be interposed between the longitudinal and transverse members I 4 and I8 respectively.

As illustrated in Fig. 2, the ends of the members l4, l6, l8 and 20 forming the framework may be shaped'to lie adjacent the upper surface of the master-male model It). It is not necessary-that the distance between the ends of the segments l4, l6, l8 and and the surface of the master male model be uniform, and it is not necessary that the ends of the members forming the framework conform to the shape of the master male model.

As illustrated in Fig. 2, the ends of the segments H, I, I8 and 20 adjacent the working surface of the master male model It) may be provided with suitable anchorage means such for example as small nails 22 having their heads 24 spaced 9, suitable distance from the ends 26 of the segments. When the framework has thus been positioned suitable masking or facing material may be positioned adjacent the edges of the segments of the framework and. the surface of the master male model to blank off or seal the space between the ends of the segments and the surface of the male master model.

Suitable alloyof the Wood's metal group which liquefies at a temperature sufficiently low as not to burn the surface of the master male model may be poured into-the blanked-off space between the lower ends 26 of the segmental frame and the uppersurfaceof the master malemodel. The molten alloy solidifies rapidly because of the fact that it is relatively thin and has large surface contact. An alloy face 28 accurately conforming to the size and shape of the surface of the master male model is thus formed. The ends 24 of the nails If desired, suitable plugs 30 having alloy faces ll conforming to theshape of the surface of the master male model M may be inserted in the apertures between the segments I4, IG IB and 20 wherebythe female checking fixture 8 will embody a continuous smooth surface corresponding to the surface of the male master model II) which may be usedfor spotting purposes, for Kellering female pads, or for the reproduction of duplicate male models. The surface of the block 30 adjacent the upper surface of the male master .model .IO need not accurately conform to the shape and size of the surface of the master model and does not necessarily have to be a predetermined distance therefrom. When in proper place. suitable liquid alloy of the Wood's metal group may be poured through apertures in the block 30 to fill the space between the block 30 and the upper surface of the master model thereby accurately reproducing the shape and dimensions of themaster model on the alloy face II of the block 30. Suitable fastening means such for example as nails 32 may be employed to fasten the cast material N tothe block 30. a s

The block 30 may be removablyattachetto the framework of the checking fixture in any de sired manner such for example as by dowel pins 34. The block 30 may also be fastened in place by means of a block 36 positioned to overlie a portion of the framework of the checking fixture in such a manner that dowel pins 38 or other suitable attaching means may be projected through the block as into the block 30 to suitably interconnect the two members.

-Where it is desired to pierce certain aperturesin the finished panel, a plate 40 made of steel or other suitable material and having a developed hole 42 therein may be suitably fastened in the checking fixture and held in place by the alloy face which preferably overlies a portion of the bevelled edge 4| of the plate 40. The plate 40 may be removed from the model and fastened in any suitable manner such for example as by wood screws in the impression which has been made through casting the metal over the plate between the fixture and the master model.

Suitable loose pieces 44 may be screwed and doweled or otherwise fastened to the main fixture 8. The loose pieces 44 may be shaped to embody a desired form to correspond with a desired contour of the master wood model or development and which extends to a desired flange or trim line.

A block of wood or other suitable material 46 may be employed to definitely locate apertures such for example as the window opening I 2. The vertical side of the block 46 is preferably utilized to establish the flange line of the window opening in the die.

In the event that it is desired to use an alloy or metal which is harder than an alloy of the Wood's metal group, the framework of the checkingfixture may be fabricated and the space between the checking fixture and the master model may be filledin by spraying an alloy or any suitable metal with the oxyacetylene gun. If. this expedient is resorted to the space between the segments of the checking fixture should be relatively .small. so that the sprayed surface forming the checking fixture will be supported at suitable points. After the space between the checking fixture and the master model has been thus filled in and the space between the segments of the checking fixture has been built up to a desired degree, it may be desirable" in certain types of work to add suitable reinforcing material such for example as molten alloy or metal introduced above the sprayed surface to strengthen and rigidity the surface of the sprayed checking fixture.

My improved fixture is particularly desirable in the building of dies for sheet metal stampings because it provides an accurate female duplication of amaster model with all the necessary developments and conditions embodied therein. All of the'dies employed to'perform a series of operations necessary to form one finished stamping can therefore be checked on the one fixture since it has all the necessary developments and conditions which will be transferred from the fixture to the 'dies. Each die following in its proper order will therefore perform the necessary operation and will be in proper relation to the preceding and following operationsi The human error heretofore occasioned by reason of the fact that one group of men work on one die of a series while another group of men work on another die of the series'is largelyeliminated. The operations for one stamping will follow through accurately and without error from the preceding die or operation and each die will have the correct dimensions and shape thereby assuring that when' a panel is made or formed on a die it will have the proper shape and dimensions to fit perfectly in connection with the next operation which in turn is developed from the same master fixture whose parts naturally always have all the necessary developments in proper location with the rest of the panel.

These fixtures e te many longer methods of obtaining a certain accurate development or condition on a die, such for example as making extra templets and surface plate lay-out work and the establishment of a certain point from the fixture to a die. It is relatively easy to check the stampings at "various operations, and since the various dies can also be readily checked on the same fixture, considerable time and effort is saved and the work can be carried on more accurately than has heretofore been possible. 4

The use of the fixtures. with the inserted plugs naturally gives. a much more accurate surface for spotting and Keliering than heretofore used in the making of so-called "Keller plasters or any type female plaster cast. This type of fixture due to its accuracy and complete coverage of all conditions on sheet metal stamping dies decreases the number of skilled men required to perform the operations because the human error is largely eliminated from the time the fixture is first put into use until the time that all of the dies in a series of operations are completed.

I claim:

1. That method of. fabricating a checking fixture conforming to the shape of a master model which comprises building up a framework of side and cross members generally, conforming to the shape of the master model, applying alloy retaining means to a surface of the framework, masking off the space between said members and the master model, introducing molten Woods metal alloy between said members and the master model to form a checking surface, removing the framework and alloy checking surface from the master model when the alloy solidifies, introducing removable plugs having surfaces generally conforming to the shape of the master model in the spaces between said members, applying allo'y retaining means to'a surface of said plugs. introducing molten Woods metal alloy between said plugs and master model a checking surface, and removing the the master model when to form checking fixture from the alloy solidifies.

2. The method of forming a female checkingfixture having means to locate flange and trim lines which comprises superimposing a framework on a master male model in such a manner that a free space of small dimension having large surface area per unit of volume is interposed between the bottom of the framework and the surface of the master model, positioning retaining means such as nails'in the framework with their, heads projecting into the free space, introducing molten alloy of the Woods metal group, into said free space to engage the heads of the nails and bond the alloy to the framework, and removing said framework and alloy from the master model when the alloy solidifies for use as achecking fixture.

3. That method of fabricating a skeleton checking fixture having means to locate flange and trim lines and conforming to the shape of a wood master model which comprises building up a framework of side and cross members generally conforming to the shape of the master model,

applying alloy retaining means to a surface of the framework, masking off the space between the members of the framework and the master model, introducing molten alloy of the Woods metal group between said members of the framework and the master model to form a checking surface of the checking fixture accurately conforming to the contour of the master model without burning or otherwise scoring the master model, and removing the skeleton checking fixture from the master model when the alloy solidifies.

4. That method of forming posing on the master model a wood framework having portions terminating'adjacent the surface of the master model whereby a free space having large surface area per unit of volume lies between the master model and the adjacent portions of the framework, introducing alloy retaining means into the portions of the framework positioned to lie adjacent the master model in such a manner that a portion of the alloy retaining means projects into the space between the framework and master model, masking off the space between the portions of the framework and the master model, completing the die fixture by casting into the masked ofl space an alloy having such low melting point that it will flll the space between the surfaces of the adjacent portions of the framework and the surface of the master model withoutinjuring said surfaces and engage the alloy retaining means and solidify with negligible shrinkage thereby providing the framework with a surface accurately conforming to the contour of the master model.

5. That method of'forming from amaster male model a female checking fixture having all necessary flange and trim lines pierced holes and all contours and shapes of the master model which comprises superimposing on the master model a wood framework adjacent the surface of the master model whereby a free space having relatively large surface area per unit of volume lies between the master model and the adjacent portions of the framespace between the portions of the framework and the master model, completing the female checking fixture to the inside of metalby casting into the masked of! space an alloy having such low melting point that it will fill the space between thesurfaces of the adjacent portions of the framework and the surface of the master model:

without injuring said surfaces and engage the outwardly flared projections of the retaining means and solidify with negligible shrinkage thereby providing the framework with a checking surface accurately conforming to the contour of the master model.

6. That method of forming a female die fixture to the inside of metal from a master male model formed to the outside or metal which coma die fixture from a master wood model which comprises superimhaving portions terminating prises superimposing on the master male model a framework having portions terminating adjacent the surface of the master model whereby a relatively narrow free space having large surface area per unit of volume lies between the master model and the adjacent portions of the framework, introducing retaining means into the portions of. the framework positioned to lie adjacent the master model in such a manner that the retaining means projects into the space between the framework and master model, masking oil the space between the portions of the female die fixture by casting into the masked oil framework and the master model, completing the r -master model and the contour-receiving base a space an alloy having such low melting point 15 that it will fill the space between the surfaces of "the adjacent portions of the framework and the surface of the master model without injuring said surfaces and engage the retaining means and rapid chilling caused by the large surface area per unit of volume between the framework and the master model thereby providing the framework with-a surface accurately conforming to the contour of the master model. 7

' solidify with negligible shrinkage because of the 2 0 material which will form therebetween completely and subsequently harden with negligible shrinkage to form a die fixture having an external surface accurately conforming to the contour oi the master model, which material is characterized by flowing and hardening under temperature and liquid conditions which are not damaging to the material of the mastermodel, and retaining said material'to the receiving base by retaining means projecting from said material into the base.

HARVEY G. GROEHN. 

